Today, let's look at alchemy. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.

When we think of alchemy, we
think of magicians trying to change lead into gold.
Yet alchemy was actually the study of chemistry
from the 3rd century BC all the way through the
next 2000 years. The word probably comes from the
Greek chemeia, which meant to
transmute or change matter; and that's what
alchemy, like chemistry itself, has always been
concerned with.

Alchemy originated when Aristotle took up an older
idea that all matter combined the four elements of
earth, air, fire, and water. He guessed that these
elements could be changed -- transmuted -- by the
action of heat and cold, or dampness and dryness.

Aristotle's ideas were developed first by the
Greeks after him, and then by Arab scientists. From
time to time, alchemy mired itself in metaphysical
razzle-dazzle. The practical Romans had no taste
for it at all. So, as civilization spread north
into Europe, alchemy all but vanished until the
13th and 14th centuries, when scholars began to
reread the old Greek and Arabic texts.

Of course, alchemy promised great wealth to anyone
who figured out how to transmute other metals into
gold. It might seem a waste that so many alchemists
devoted their lives to that, but the spin-off was
enormous. By trying to understand transmutation,
they learned about practical metallurgy, about
extracting metals from ores, and about chemical
reaction. Their results were reported in terms
alien to our ears, but the late medieval chemists
were suprisingly able metallurgists.

Late-17th-century chemists saw matter as made up of
three elements, or "earths," as they were called:
Vitreous earth gave solidity to matter; fluid earth
gave it liquidity; and fatty earth, which was later
called phlogiston, gave it
combustibility. These were the old Aristotelian
elements of earth, water, and fire -- without air!
Air was thought to be inert and not a part of other
materials.

All the while, a more and more analytical science
was being built on these ideas. The alchemical view
of matter didn't give way to an atomic theory until
less than two hundred years ago. And then it didn't
give way completely. When people realized that heat
wasn't a part of matter, they replaced phlogiston
with caloric. Caloric was another
Aristotelian substance that occupied all matter and
flowed from hot bodies to cold ones. Even after the
atomic theory of matter replaced the various
earths, caloric was still being used to describe
heat when my grandfather was a little boy.

So before we write alchemy off as voodoo magic,
we'd better ask what our own chemistry will look
like in the 22nd century.

I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.